Electro-magnetic door holder



y 0, 1968 N. J. VIETZ 3,394,427

ELECTRO-MAGNETIC DOOR HOLDER Filed Aug. 26, 1966 SOURCE FIRE DETECTION SYSTEM INVENTOR. FIG 4 NORMAN J. VIETZ ATTORNEY.

United States Patent "ice 3,394,427 ELECTRO-MAGNETIC DOOR HOLDER Norman J. Vietz, Brooklyn Center, Minm, assignor to Honeywell Inc., Minneapolis, Minn., a corporation of Delaware Filed Aug. 26, 1966, Ser. No. 575,364 6 Claims. (Cl. 1648.5)

ABSTRACT OF THE DISCLOSURE An electromagnetic door holder having a wall mounted electromagnet and an associated door mounted armature having an adjustable center portion permitting variations of the magnetic holding power.

This invention is related to a door holder and more particularly to an eletcromagnetic door holder which holds a door in the open position against the pull of a door closer and which allows the door to be released and close when an emergency condition arises. This invention is particularly adapted for use with fire or smoke doors in which it is desired that the means for holding the door open also includes an arrangement for automatically releasing the door. It is well recognized, of course, that it must be possible to manually pull the door away from the electromagnetic door holder while it is energized. This is required so that individual doors in a building may be closed when necessary without turning off the door holding system. It has been found that where many electromagnetic door holders are used in the same building which may include use on doors of different sizes and utilizing door closers of varying size, it is desirable to be able to adjust the holding power of the individual door holder. This invention is more specifically related to an electromagnetic door holder having an adjustable holding power.

Turning now to the drawing:

FIGURE 1 is a diagrammatic representation of an electromagnetic door holder system of my invention as installed on a swinging door.

FIGURE 2 is a cross-sectional view of the electromagnetic assembly and of the armature assembly.

FIGURES 3 and 4 are further views of the armature assembly.

Referring now to FIGURE 1 there is disclosed generally at an eletcromagnetic door holder having an electromagnet portion 11 mounted on the wall and an armature portion 12 mounted on a swinging door 13, which door is also equipped with a conventional door closer 14. Upon opening of the door the armature 12 is brought into contact with the eletcromagnet core to hold the door open. While the door holder is shown holding the door open ap proximately 180, it obviously may be mounted to hold the door at 90 or other desired angles. A pair of conductors 17 connect the electromagnet to a source of power through a switch 18. Switch 18 may be controlled by a signal from a fire detection system 19, if desired.

In FIGURE 2 the electromagnet 11 is shown in greater detail in cross section fastened to the wall and comprises a winding and a magnetic core 16. The electromagnets are powered by DC or by AC converted to DC by a simple bridge rectifier.

The adjustable holding power of the door holder is obtained by the novel construction of the armature 12. As can be seen in FIGURE 2, the armature is of concentric construction and has :a threaded adjustable center portion 20 which screws into the threaded bore in armature body 12 so that its face 21 can be adjusted relative to the plane of the face 22 of armature 12. The holding 3,394,427 Patented July 30, 1968 power is reduced as the center portion 20 is screwed farther into body 12, due to the increasing air gap in the magnetic flux path between armature portion 20* and magnet core 16. The armature portion 20 is adapted to be adjusted by the use of an Allen wrench or the like.

In operation it is the usual condition that the door holders are installed on the many fire and smoke doors of a large building. They are capable of holding open both hinged doors (as shown) and sliding doors. When power is applied to the door holder electromagnetic portion 11, a magnetic force is applied to the matching door plate armature 12 to hold the door in the open position. Interrupting the power to the holder removes the holding force and thus the door is released by breaking the elec; trical circuit to the door holder coil 15. The door is then closed by other door closer equipment. The door holder must overcome the force of the door closer when the door holder is energized.

It is desired that the holding force should be adjustable to compensate for the variety of door sizes and weights and the different sizes and forces of door closers with which the door holder cooperates so that the manual eifort required to overcome the door holder may be easily controlled. Maximum holding power is achieved when the armature face including outer face 22 and the inner or center face 21 make contact with the metal core 16. Holding power decreases as an air gap is introduced in the magnetic path. In order to adjust the holding force, the air gap between core 16 and inner or center face 21 is changed in dimension. The center portion 20 of the armature is threaded to screw into the main body of armature 12 and this allows precise control of the air gap and thus the holding power. The mounting assembly for the armature shown in FIGURES 2, 3, and 4 also provides for horizontal and vertical alignment of the armature face to properly mate with the electromagnet.

Modifications of my invention will be apparent to those skilled in the art and the invention is not intended to be limited by the drawing but only by the scope of the appended claims.

I claim as my invention:

1. In an electromagnetic door holder for normally holding a door in an open position, the door holder comprising:

eletcromagnetic flux generating means having a pair of poles defining an air gap, said means positioned in the path of travel of the door as it is moved to an open position; and

adjustable armature means fastened to said door, for

substantially closing said air gap when said door is in said open position, said armature means having a first portion adapted to come into contact with a first pole of said flux generating means and having a second portion, adjustable with respect to said first portion, adapted to come into proximity with the second pole of said flux generating means thereby defining a minor air gap, said adjustable armature portion thereby controlling said minor air-gap length.

2. The structure defined by claim 1, wherein said first and second portion of said armature means are concentric.

3. The structure defined by claim 2, wherein one of said concentric armature portions is threaded to screw into a threaded bore of the other portion to thereby provide for adjustment of said armature means.

4. The structure defined by claim 1, wherein said second portion of said armature means is threaded and screws into a threaded bore in said first portion whereby the effective face of said second portion can be adjustably recessed with respect to the armature face of said first portion.

5. Apparatus as defined in claim 1, and means including switch means-connecting terminals of an-electrical sourcein energizing relation to said electromagnetic flux generating means 6. The combination as defined in claim 5, wherein said switch means is connected to and operated in response to a signal from fire detection means to provide automatic release of said door holder.

3,232,654 2/1966 Israelson et al. 33S295 X 3,284,840 11/1966 Ulman l6-48.5

BOBBY GAY, Primary Exanziner,

J. L; KOHNEN, Assistant Examiner. 

